1. Field of the Invention
The present invention relates to a direct ink supply writing implement. More particularly, the present invention relates to a direct ink supply writing implement arranged to directly accumulate ink in an ink tank and having an ink reservoir made of a porous material and disposed between a nib and the ink tank so that ink discharged when the pressure in the ink tank has been raised is temporarily stored in the ink reservoir. In the present invention, note that the expression "front" means a portion adjacent to the nib and the expression "rear" means a portion adjacent to the ink tank.
2. Description of the Related Art
(a) Examined Japanese Utility-Model Publication No. 56-33739
In the publication (a), an implement for writing has been disclosed which incorporates a nib secured to the leading end of a barrel. Moreover, an ink reservoir disposed in contact with the rear end of the nib and having a capillary action is inserted into the inner surface of the barrel such that a ventilation passage connected to the outside air exists from the inner surface of the barrel. In addition, a compressed member is joined to the rear end of the ink reservoir to raise the density of the capillary spaces in the ink reservoir at the foregoing joint portion. Moreover, the rear end of the ink reservoir and the ink tank formed in the rear portion of the barrel are connected to each other through a communication hole.
However, the implement for writing in the publication (a) is an implement for writing of a type having a structure that ink supplied from the ink tank is temporarily absorbed by the ink reservoir so as to consume absorbed ink from the nib. Therefore, in the implement for writing in the publication (a), ink in the ink tank is not directly supplied to the Nib through an ink guide member or the like. Therefore, the quantity of ink which is discharged from the nib is insufficient. Thus, script becomes too light and faint and patchy. Therefore, smooth writing for a long time is not permitted.
Although the implement for writing in the publication (a) has the close capillary spaces in the rear end portion of the ink reservoir because of the compression, the other main portion has straight capillary spaces. Therefore, the widths of the capillary spaces (that is, the capillary forces) are substantially uniform. It leads to a fact that a major portion of ink stored in the ink reservoir can easily be concentrated to a lower portion of the ink reservoir (that is, a front portion of the ink reservoir) when downward attribute of the nib is maintained. As a result, there is apprehension that ink reservoir leaks outwards by dint of an impact which is made when the implement for writing is dropped or when a cap is removed.
Since the implement for writing in the publication (a) easily encounters concentration of ink in the front portion of the ink reservoir, ink in the front portion of the ink reservoir cannot smoothly be returned into the ink tank when the pressure in the ink tank is reduced owning to change in the temperature. Therefore, air can easily be introduced into the ink tank in a state in which ink is retained in the front portion of the ink reservoir. It leads to a fact that ink left in the front portion of the ink reservoir is gradually increased if expansion and contraction of air in the ink tank are repeated. Thus, there is apprehension that ink leaks through the leading end of the nib.
What is worse, the implement for writing in the publication (a) has the arrangement that a major portion of accumulated ink is distributed in the front portion of the ink reservoir and air can easily be introduced into the rear portion of the ink reservoir. Therefore, an air duct connected to the outer air must be formed between the outer surface of the ink reservoir and the inner surface of the barrel. If the air duct is omitted, there is apprehension that ink is undesirably discharged to the outside when air in the rear portion of the ink reservoir is expanded by dint of, for example, rise in the temperature. Therefore, the implement for writing in the publication (a) has the above-mentioned air duct to prevent a fact that air is confined in the rear portion of the ink reservoir. Thus, leakage of ink is prevented.
However, the air dust cannot easily be formed between the inner surface of the barrel and the outer surface of the ink reservoir. Thus, the manufacturing cost is enlarged. If the members including the barrel are made of molded synthetic resin, making of an air duct groove and rib causes surface sink to take place on the outer surface of the barrel. Thus, there is apprehension that the quality of the appearance deteriorates and airtightness which is realized when the cap is put becomes unsatisfactory.
(b) Unexamined Japanese Utility-Model publication No. 2-48377
In the publication (b), an implement for writing having an ink guiding member disposed between an ink tank and the nib has been disclosed. According to the foregoing disclosure, a porous member for adjusting ink in an implement for writing is arranged such that the capillary force of the porous member (corresponding to the ink reservoir according to the present invention) disposed in contact with the ink guiding member and arranged to surround the same is enlarged in a portion adjacent to the ink guiding member. Moreover, the capillary force is reduced in the outer portion.
In the implement for writing in the publication (b), even if the capillary force of the ink reservoir is changed in the radial direction such that it is enlarged in the portion adjacent to the ink guiding member and the same is reduced in the outer portion, the capillary force is uniform in the axial direction. Therefore, if the downward attitude of the nib is maintained, ink is concentrated to the front portion of the ink reservoir similarly to the implement for writing in the publication (a). Thus, there is apprehension that ink is leaked when an impact is made because of drop of the implement for writing or when the cap is removed.
(c) Examined Japanese Utility-Model Publication No. 37-12939
In the foregoing publication (c), a fountain pen type felt pen has been disclosed which incorporates an ink cylinder which includes an ink tank, an ink reservoir disposed in front of the ink tank and formed by felt chips or cotton and a partition wall arranged to insulate the ink reservoir and the ink tank from each other and having a small communication hole. Moreover, an ink guiding member made of elongated felt subject to a resin process penetrates the partition wall and the ink reservoir.
In the direct ink supply writing implement in the publication (c), the overall capillary force in the ink reservoir is uniform. Therefore, if the foregoing implement for writing is stored for a long time in a state in which the nib faces downwards, ink can easily be concentrated to the front portion of the ink reservoir. Therefore, there is apprehension that ink leaks by dint of an impact which is made when the implement for writing is dropped or when the cap is removed.
What is worse, in the direct ink supply writing implement in the publication (c), ink can easily be concentrated to the front portion of the ink reservoir. Moreover, contact between the outer surface of the ink guiding member and the inner surface of the ink reservoir is instable, causing smooth return of ink in the front portion of the ink reservoir into the ink tank to be inhibited when the pressure in the ink tank has been reduced because, for example, the temperature has been changed. Therefore, air can easily be introduced into the ink tank in a state in which ink is left in the front portion of the ink reservoir. If expansion and contraction of air in the ink tank are repeated, residual ink in the front portion of the ink reservoir is gradually increased. As a result, ink leaks through the leading end of the nib.
The direct ink supply writing implement in the publication (c) is a direct ink supply writing implement having the structure that the ink tank and the nib are directly connected to each other through the ink guiding member without the ink reservoir. Therefore, satisfactory ink discharging characteristic can be realized as compared with a type in which the ink guiding member does not penetrate the ink reservoir. However, the realized ink discharging characteristic is insufficient to realize satisfactory ink leakage preventing characteristic.
The reason for this lies in that accurate and uniform capillary space size cannot easily be realized if uniform distribution of capillary space sizes is required. Therefore, the capillary space sizes easily vary. Capillary spaces having large sizes cannot serve as the portion for temporarily store ink. The excessively large capillary spaces deteriorate the overall performance of the ink reservoir for storing ink. Thus, undesirable ink leakage easily takes place. To form an effective ink storage portion in the overall body of the ink reservoir, dense capillary spaces are required. Therefore, the direct ink supply writing implement in the publication (c) inevitably has the structure having the dense capillary spaces in the ink reservoir in order to realize a satisfactory ink leakage preventive characteristic. As a result, air cannot smoothly be introduced into the ink tank, the pressure of which has been reduced. As a result, the ink discharging characteristic from the nib deteriorates. Thus, script becomes too light and faint and patchy.
What is worse, the direct ink supply writing implement in the publication (c) incorporates the ink guiding member which has a simple structure made of the porous material. Therefore, a limit is imposed to quickly and sufficiently supply ink from the ink tank to the nib.
(d) Toku Hyo Hei. No. 6-510491
In the publication (d), a direct ink supply writing implement has been disclosed which has a structure that an ink guiding member is in contact with an ink reservoir in a direct manner. Moreover, the ink guiding member is received in a central hole of a partition wall to close the central hole. A gap (corresponding to the communication hole according to the present invention) exhibiting capillary force superior to that of the ink reservoir and having a function of exchanging air and ink is formed.
In general, the gap limits communication of ink and air between the ink tank and the ink reservoir by dint of the size of the gap. Therefore, a significant accuracy is required for the gap to exchange air and ink.
If the size of the gap is too large, the capillary force is weakened. Thus, smooth return of ink from the ink reservoir to the ink tank is inhibited when the pressure in the ink tank has been reduced. Thus, outer air is introduced into the ink tank in a state in which ink is left in the ink reservoir, causing the state in which the pressure in the ink tank has been reduced to be canceled. If the internal pressure in the ink tank is raised, the ink storage portion cannot satisfactorily store overflowed ink. Thus, there is apprehension that ink leaks from the nib.
If the size of the gap is too small, the capillary force is strengthened. Thus, introduction of air into the ink tank in a pressure reduced state is prevented, causing smooth exchange of air to be prevented. As a result, the pressure reduced state in the ink tank cannot be canceled. Therefore, the quantity of ink which is discharged from the nib is gradually reduced after consumption of ink has been started. It leads to a fact that script becomes too light and faint and patchy.
Since the direct ink supply writing implement in the publication (d) incorporates the ink guiding member which is made of the porous material, such as a fibrous material, the sizes of the plural gaps in the ink guiding member received in the central hole in the partition wall considerably vary. Among the gaps, a largest gap serves as the communication hole for air duct according to the present invention.
To prevent undesirable leakage of ink from the nib because ink is left in the ink reservoir, the largest gap which serves as the communication hole, must have a small size. In consideration of the variation of the gap sizes, the capillary spaces in the ink guiding member which is received in the central hole must considerably be made densely. As a result, the capillary force of the communication hole is enlarged excessively. Thus, outer air cannot easily be introduced into the ink tank in the pressure reduced state. Therefore, the pressure reduced state in the ink tank cannot sufficiently be canceled. Thus, the ink discharging characteristic from the nib gradually deteriorates after consumption of ink has been started.
Since the ink guiding member of the direct ink supply writing implement in the publication (d) is made of the porous material, such as the fibrous material, the overall body has great capillary force. Therefore, a satisfactory large quantity of ink cannot quickly be supplied to the nib. Thus, script becomes too light and faint and patchy.
(e) Examined Japanese Utility-Model Publication No. 55-32787
In the publication (e), a structure has been disclosed in which a communication hole is formed between the outer surface of an ink guiding member. (specifically, a pen member made of a fiber bundle core or an open-cell plastic core) and the inner surface of a central hole of a partition wall having an axial groove.
In the above-mentioned structure (that is, the communication hole is formed between the outer surface of the ink guiding member and the inner surface of the central hole in the partition wall), the ink guiding member is made of fiber or a porous material, such as the open-cell synthetic resin member. Therefore, when the ink guiding member is disposed and secured in the central hole in the partition wall, the outer surface of the ink guiding member is expanded in the groove in the inner surface of the central hole in the partition wall. Therefore, there is apprehension that the communication hole is closed or the communication hole is reduced. Thus, appropriate gap size in the communication hole cannot be realized.